Dismutation of olefins

ABSTRACT

USING AS A CATALYST MOO3-RE2O7(WEIGHT RATIO APPROXIMATELY 10:1) ON AN ALUMINA SUPPORT IT IS POSSIBLE TO CARRY OUT DISMUTATION REACTIONS OF C2-C20 ACRYCLIC MONOOLEFINS AT LOW TEMPERATURES AND MUCH SMALLER AMOUNTS OF RE2O7 THAN ARE CONVENTIONALLY NECESSARY, E.G, PRIOR ART REQUIRED 10 PERCENT MOO3 AT 150*C. OR 20 PERCENT RE2O7 AT 38*, WHEREAS THE PRESENT INVENTION REQUIRE 10 PERCENT MOO3-1 PERCENT RE2O7 AT 38*C. TO GIVE HIGHER CONVERSION AND YIELDS. BY MODIFYING THIS CATALYST WITH A SMALL AMOUNT OF FLUORIDE ION ISOBUTYLENE WHICH OTHERWISE IS SUBJECT TO OLIGOMERIZATION CAN BE DISMUTATED WITH C3C20 ACYCLIC MONOOLEFINS. THE PRODUCTS ARE DIFFERENT AND MORE DEIRABLE OLEFINS THAN THE STARTING MATERIALS.

United States Patent U.S. Cl. 260683 D 16 Claims ABSTRACT OF THEDISCLOSURE Using as a catalyst MoO -Re O' (weight ratio approximately:1) on an alumina support it is possible to carry out dismutationreactions of C C acyclic monoolefins at low temperatures and muchsmaller amounts of Re O than are conventionallynecessary, e.g., priorart required 10 percent MoO .at 150 C. or 20 percent Re O at 38; whereasthe present invention requires vl0 percent MoO -1 percent Re O at 38 C.to give higher conversion and yields. By modifying this catalyst with asmall amount of fluoride ion isobutylene which otherwise is subject tooligomerization can be dismutated with C C acyclic monoolefins. Theproducts are different and more desirable olefins than the startingmaterials.

This is a division of application Ser. No. 844,207, filed July 23, 1969,now issued as U.S. Pat. No. 3,702,827.

BACKGROUND OF THE INVENTION The reaction of olefinic molecules in thepresence of metal containing catalysts to produce an equal number ofother olefinic molecules, e.g. propylene passed over amolybdenum-alumina catalyst to yield as the principal products ethyleneand butenes by the reaction o-oio is often referred to asdisproportionation and can be attributed to Robert L. Banks and Grant C.Bailey, I&EC Product Research and Development, vol. 3, No. 3, September1964, pp. 170-173. The term dismutation has also been employed todescribe this reaction and is the term used herein-to describe thereaction of olefinic molecules to produce an equal number of otherolefinic molecules. i

In addition to reaction of a single molecule type as described by Banksand Bailey, there has been considerable interest in a variation of thisprocess wherein two dissimilar olefin molecules are reacted to form twomolecules of a different single olefin, e.g. ethylene and 2-butene reactto form propylene. This variation is shown in Netherlands patentapplication 6,514,985 of British Petroleum Company, Limited, publishedMay 20, 1966.

Dismutation of olefinic materials offers anew vista of synthesis ofvaluable olefin monomers from less valuable olefin monomers. By thenovel combination of the present invention a synergism resulting in lowtemperature dis mutation has been obtained. It was shown in commonlyassigned application Ser. No. 819,945 filed Apr. 28, 1969, now Pat. No.3,697,613, that the oligomerization of isobutylene could be inhibitedand the dismutation of is0 butylene and an acyclic olefin having 2 to 20carbon atoms coulde be obtained by treating alumina supported oxides ofmolybdenum, tungsten and rhenium with a soluble fluoride salt. Thetungsten and molybdenum oxide catalysts required relatively hightemperatures whereas the rhenium oxide catalyst operated at much lowertemperatures, but required higher catalyst concentrations. Lowtemperatures and low rhenium oxide concentration are achieved by theinvention described as follows.

3,792,108 Patented Feb. 12, 1974 ice DESCRIPTION OF THE INVENTION It hasnow been found that the dismutation of olefins can be carried out at lowtemperatures over a novel molybdenumoxide-rhenium oxide catalyst.Briefly stated, the present invention is a process for the dismutationof olefins in the presence of a catalytic composition comprising rheniumoxide on molybdenum oxide or mixtures of rhenium oxide and molybdenumoxide on a support comprising a major proportion of alumina. A secondaspect of the present invention is the novel catalyst which allows theuse of very low temperatures and only a fraction of the rhenium oxidepreviously employed.

In regard to isobutylene which has a tendency to oligomerize under theconditions and with the catalysts that produce dismutation reactionswith other olefins it has now been found that the oligomerization isinhibited and the dismutation of isobutylene and a C to C olefin can becarried out at low temperatures over a molybdenum oxide-rhenium oxidecatalyst which has been treated with a fluoride salt. Briefly stated,this aspect of the present invention'is a process for the reaction of2-methyl-l-propene and an olefin comprising contacting2-methyl-1-propene and an olefin having at least 3 carbon atoms in thepresence of a catalytic composition comprising rhenium oxide andmolybdenum oxide on a support of a major proportion of alumina saidcatalytic composition incorporating a modifying amount of fluoride ion.

Another aspect of the present invention is the fluoride catalyst whichis a composition comprising rhenium oxide and molybdenum oxide on asupport comprising a major proportion of alumina said catalystincorporating a modifying amount of fluoride ion.

Reactants Suitable olefins for the dismutation reactions are typicallyacyclic monoolefins having 2 to 20 carbon atoms and include, forexample, ethylene, propene, l-butene, 2- butene, l -pentene, Z-pentene,3-hexene, 4-methyl-1-heptene, Z-de'cene, 6 -dodecene, 3-tetradecene,l0-eicosene and thelike. A preferred class of olefins has up to 10carbon atoms and a still more preferred class would have up to 6 carbonatoms. Since there is tendency for isobutylene to oligomerize with theunmodified MoO -Re O catalyst, it is not a preferred reactant with thatcatalyst, however, modification of the MoO -Re O -alumina catalyticcomposition as indicated hereinafter with fluoride ion inhibits thistendency to oligomen'ze. In the dismutation of isobutylene either withitself or other olefins it should be noted that the olefin should haveat least 3 carbon atoms. Etheylene will, of course, react withisobutylene; however, the products are the same as the startingmaterials. One embodiment of the present invention relates to thepreparation of 2-methyl-2-butene from 2-methyl-1-propene and 2-butenein, a fluoride modified system. In this embodiment the reaction can berepresented as:

2-methyl-2-butene is of value as the immediate precursor of isoprenewhich is obtained by the oxydehydrogenation of 2-methyl-2-butene.Isoprene is of value in the preparation of synthetic rubbers. The otherproduct of this reaction is propene which polymerizes alone topolypropylene or with other olefin monomers such as ethylene to produceethylene-propylene co-polymers which have wide usefulness such as films,fibers and coatings.

In addition to the utilities for 2-methyl-2-butene and propene listedabove, the olefinic products of the dismutation reactions describedherein for the most part,

have established utility as precursors of polymers. The olefinicproducts are hydrated by conventional means to produce polyhydricalcohols which are employed in the preparation of polyurethanes andpolyesters, formed by the condensation, respectively, of polyisocyanatessuch as toluene diisocyanate and polybasic acids such as terephthalicacid with the polyols so produced.

Catalysts The catalyst employed in the process of the inventioncomprises a catalyst support, an oxide of molybdenum and an oxide ofrhenium. The metal catalyst composition component comprises the oxidesin a high positive oxidation state, e.g. hexavalent molybdenum andheptavalent rhenium. Preferably M is added to support first with Re Odeposited thereon; however, the two can be added at the same time as amixture. When the catalyst is employed in some other form, pretreatmentis customarily employed to convert the molybdenum and rhenium to theform of the oxide. The proportion of molybdenum can be varied, generallyfrom about 2.0 to 30 weight percent, with the more preferable proportionbeing in the range of to 20 weight percent calculated as the metal oxideon the support. The rhenium oxide is deposited into the molybdenum oxidein quantities, for smaller than would be necessary for rhenium oxidealone. In order to obtain the benefits of the present invention aslittle as 0.5 weight percent rhenium oxide can be employed. Because ofthe unpredictable and enhanced effect of the combination of rheniumoxide on M00 it is not necessary to use large quantities of rheniumoxide. Generally, no more than 1.5 weight percent rhenium oxide isnecessary to obtain optimum results although larger quantities up toweight percent can be employed. The weight ratio of rhenium oxide tomolybdenum oxide can vary widely but is generally in the range of 1:60to 5:1. In the past, great care had to be taken in handling the rheniumoxide since it sublirnes at around 450 C. It is quite common to lose agood portion of the rhenium oxide catalyst when it is employed at itsconventional concentration of around percent. It has been found there islittle if any rhenium oxide lost when the small amounts employed incombination with molybdenum oxide are used.

Suitable supports are high surface area inert materials. Particularlysuitable supports comprise at least a major proportion of alumina withno more than minor proportions of other components, specifically asuitable catalyst support contains at least 75 weight percent alumina,preferably 95 weight percent alumina with the remainder being made ofessentially inert materials, such as silica 0r magnesia which do notsubstantially promote undesirable side reactions.

In the reactions of isobutylene a feature of the invention process isthe incorporation of fluoride ion into the alumina supported, oxide ofmolybdenum-rhenium oxide catalyst. The fluoride ion is incorporated in areduced amount from that formerly needed. In order to modify theprevious catalysts, i.e. molybdenum oxide, tungsten oxide or rheniumoxide on alumina, fluoride ion was incorporated into the catalyst in aweight ratio of F- to metal oxide in the range of .065 :1 to 0.20:1. Thepresent catalyst, however, will not tolerate this amount of fluoride andis deactivated. By the term modifying amount is meant an amountsuflicient to inhibit oligomerization but not suflicient to deactivatethe dismutation capacity of the catalyst. When based on the total metaloxide present, i.e., molybdenum oxide and rhenium oxide this isapproximately one-tenth of the fluoride ion previously needed; or,stated otherwise, a weight ratio of fluoride ion to metal oxide presentin the range of about 0.006511 to 0.020z1. Although no mechanism isproposed to limit the present invention, it would appear that thefluoride ion is a poison to the catalyst. Thus, the maximum amount offluoride ion specified should not be exceeded, for to do so will totallydeactivate the catalyst.

The lower limit of fluoride ion concentration indicates the approximatepoint where oligomerization of isobutylene is inhibited sufficiently toallow more than a trace of the dismutation products. In any event it isessential that concentration of fluoride ion be in about the rangespecified in order to obtain the beneficial results of the process.

The fluoride ion is usually present on the catalyst compositions in theform of a soluble salt thereof. Some suitable salts are sodium fluoride,cadmium fluoride, zinc fluoride, potassium fluoride, and the like.

The preparation of the supported catalyst compositions is effected byconventional techniques of dry-mixing, coprecipitation, impregnation,ion exchange and the like. The catalyst compositions components areintroduced in separate stages. Although it is not critical, it ispreferred to add the fluoride salt, if any, subsequently to the othercatalyst components. It is the usual practice to pretreat or activatethe catalyst composition prior to utilization in the process. Theprecise method of pretreatment employed will depend to some extent onthe nature and form of the catalyst components. In general, however, thepretreatment comprises heating an initially prepared supported catalystin an atmosphere of non-reducing gas such as nitrogen, argon, carbonmonoxide or oxygen containing gas. One function served by thepretreatment is to convert the catalyst into the form of the oxides ifthese components were not initially provided as oxides. For example,initial catalyst components such as ammonium molybdate, ammoniumperrhenate and the like are converted to corresponding oxides by heatingin a non-reducing atmosphere.

It is desirable that at least a major proportion of the catalystcomponents initially be present in the highest oxidation state possibleand, if not, the desired elevation of positive oxidation if effected bypretreatment in the presence of oxygen, alone or in mixtures with othergases. Regardless of the initial form of the catalyst components, theformed catalyst should be maintained at elevated temperatures for atime. The pretreatment temperature is not critical and is typically inthe range of 300-750" C. Pretreatment times typically range from 1 to 12hours. Subsequent to pretreatment, the supported catalyst composition isusually flushed with inert gas to remove residual traces of oxygen oradsorbed water and returned to room or reaction temperature in an oxygenfree atmosphere. The finished catalyst is employed in any conventionalform such as powder, flakes, spheres, pellets, or the like.

A typical procedure of preparing the catalyst would be to add themolybdenum component, as ammonium molybdate, for example, to the aluminasupport and to calcine the impregnated alumina at 550 C. in air for twohours, cool the catalyst and then to add the rehenium oxide and to heatthe rhenium oxide impregnated molybdenum oxide-alumina at 550 C. in airfor about two hours. The catalyst is now cooled to reaction temperatureor room temperature and flushed with nitrogen. If the reaction feedincludes isobutylene the catalyst is treated with sodium fluoride andpretreated in air at 550 C. for one hour prior to nitrogen purging.

Reaction conditions The reaction is conducted by contacting the olefinfeed with the supported, modified or unmodified catalyst at adismutation temperature generally in the range of room temperature,about 20 C., to about C., preferably 25-50 C. Some reaction can beobtained at lower temperatures and temperatures up to or more can beemployed. Previously it had been known that rhenium oxide would operatein the temperature ranges specified herein; however, relatively largequantities of rhenium oxide were needed to obtain satisfactory resultsat such low temperature, i.e., generally around 20 weight percent. At 1weight percent of rhenium oxide on alumina no activity in regard tomonoolefins was observed even at temperatures up to 150C.Although-molybdenum.oxide I 7 EXAMPLE 2 a supported on aluminarequired lower concentrations of 'o l at l molybdenum oxide than therhemum catalyst, 1.e. 10 Preparatl n of R8207 aumma C ayst weightpercent, higher temperatures, 75150 ;C., were A fhellillm OXiQe CatalystP p y impreghat' required to activate the catalyst. Yet, by home unex- 5m y eommerelal u i a p ll ts w th Sufficient plained mechanism, thecatalyst compositions of the ammonium perrhenate (1n solution) toprovide 20 weight present invention employ only a fraction of therhenium Percent Theflium Oxide z v) on the pp The oxide previouslyemployed in cooperation with molyb- Pregflated alumina Was heated forabout hours t denum oxide at its conventional concentration to operateThe lyst Was cooled to room temperature in the process of the presentinvention at temperatures 10 n Placed Hilder hitregen- S1m11a11y, aci-ltalyst Contamsuitable for rhenium oxide but too low to elfectivelyem-. ing 1 weight percent rhenium oxide was prepared. ploy molybdenumoxide. In regard to isobutylene, the EXAMPLE 3 fluoride modifiedcatalysts have exhibited analogous behavior to the unmodified catayst inrelation to catalyst Preparahoh 0f s z 'l' catalyst yp concentration andreation temperatureh p c Portions of the MoO -alumina catalyst preparedas in 655 is typically carried out at from SP i to Super Example 1 wereimpregnated with sufficient rhenium atmospheric pressures. Suitablepressures'are in the range oxide .(inxsolution) to provide respectively0.5 weight of 1-150 atmospheres, Preferably P to 70 etmespherespercent,1 weight percent, and 1.5 weight percent rhenium The reaction isconveniently carried out as a" conoxide on the Support The 0.impregnated 0 tinuous process in a tubular reactor wherein the catalystl i was heated f about 2 hours at 55 c The i maintainedfin a fixedfluidiled Alternatively, catalysts were cooled to room temperature andplaced a batch type operation can be employed by agitating the I dnitfoggn. olefin reactants and catalyst together in a suitable reactorsuch as an autoclave. In the continuous process a convenient method ofmeasuring olefin addition is in 5 EXAMPLE 4 Preparation of halidemodified catalyst terms of weight hourly space velocity (WHSV) whichHalide modified catalysts were prepared by impregnatmeasures the weightof olefin which contacts unit weight ing the catalyst indicated in theTable I below with the of catalyst composition per hour and is in unitsof resolution indicated. After about one hour the catalyst ciprocalhours (hr.- )."It is convenient in the instant was dried at 110 C. Themodified catalyst was then process to continuously'add the olefin'feedto the replaced in a tubular reactor and heated at 550 C. for actor atconstant pressure, for example, to 1500 p.s.i., one hour.

" TABLE I Wt. percent Concen- Wt. metal oxide trate of I ratio onsupport oi halide halide Halide salt, Wt. ion: metal Run Catalyst M003Re201 salt percent oxide A M00; 10 NaF 4 .18 M00; 10 F 4 .18 M00a'RezO10 1.0 NaF .2 .008 R620! 20 Na]? 4 .086

v Aqueous. at a WH'SV typically in the range of .01 hr. to 0.10 EXAMPLES5-13 1113-1- 111 the case of a mixed olefin feed the components Theseexamples present a series of runs using as the are an addefli continuousat constant Pressurefeed propene over the unmodified catalystspreviously The reaehen Products can be recovered by com/en described.These runs were made in vertical, glass, tubular tional means, such asfractional condensation, fractional reactors i h fixed catalyst b d Ther a tor efiiuent was distillation or the llke. analyzed by gas-liquidphase chromatography (GLPC) TABLE II Catalyst Weight Weight ReactionPres- Conver- Z-buteue percent percent WHSV, temp, sure, sion of selec-MoOa R6207 hr. C. p.s.i. propene 1 tivity 2 l GLPC, based on weightpropene in feed. 2 GLPC, based on propene conversion. The followingexamples are present to further illustrate to determine weight percentpropene converted and the the invention: selectivity of the conversionto Z-butene. The reaction EXAMPLE 1 conditions and yields are set out inTable II.

EXAMPLES 14-20 Dismutation of isobutylene and Z-butene These examplespresent a series of runs using as the A Moorahlmlha Catalyst e Preparedby lmpl'egnat' feed isobutylene and 2-butene over the catalystspreviousg dry eofnmerclal alhmlna Pellets (Alcoa 4 ly described. Thereactions were carried out in vertical f sllfilelellt ammollhlmmolyhdate hydl'ate 50111- 70 glass tubular reactors through a fixed bedof catalyst. t1011) p 10 Welght Percent of molybdenum Oxide The reactorefliuent was analyzed by GLPC to determine s) Oh the pp The impregnatedalumina Was the weight percent isobutylene converted and the weightheated to 550 C. for about 2 hours under a flow of air. percent of2-rnethyl-2-butene in the product based on iso- The catalyst was thencooled to room temperature and butylene. The reaction conditions andyields are set out placed under nitrogen. 75 in Table III.

Preparation of MoO alumina catalyst TABLE III Results, percent CatalystConditions Conver- Wt. percent ot- Wt. ratio Reaction Pression of2-methyl- ":metal WHSV, temp., sure, isobu- Z-butene M003 Re2O1 oxidehr. C p.s.i. tyleno l selectivity M 0 0. 1 95 14. 7 90 0 M003, NaF 175 1150 14. 7 3O 15 M003, KF 13 1 95 14. 7 51 20 Rez01 0 25 32 14. 7 5 1Re201 O 1. 32-150 14.7 0 0 O1, NaF 086 07 38 14. 7 24 58 20 MoO3-Re2O1,NaF 008 1 38 14. 7 77 1 GLPO, based on weight of isobutylene in feed. aGLPC, based on isobutylene conversion.

EXAMPLE 21 This example shows the preparation and use of a catalystwhich is a mixture of rhenium oxide and molybdenum oxide on a support.Six grams of ammonium molybdate and 0.55 gram of ammonium perrhenate (in35 ml. H O) were deposited on 43 grams of H-lSl Alcoa alumina. Thecatalyst was generated by heating at 550 C. under air for 1 hour andcooling at 25 C. under nitro gen. Propylene was fed at the rate of WHSV.045 hr.- At 25 C. there was a trace of activity. At 60 C. theconversion was 18 percent to 2-butene and ethylene.

The invention claimed is:

1. A process for the dismutation of olefins at a temperature of up to150 C. in the presence of a catalytic composition comprising rheniumoxide on molybdenum oxide on a support or mixture of rhenium oxide andmolybdenum oxide on a support, the catalytic composition comprising from2 to 30 weight percent molybdenum calculated as the oxide and at least.5 weight percent rhenium calculated as the oxide.

2. The process according to claim 1 wherein the support is at least 75percent alumina.

3. The process according to claim 2 wherein the temperature is in therange of 20 to 80 C.

4. The process according to claim 3 wherein the olefin has up to 20carbon atoms.

5. The process according to claim 4 Wherein the olefin has up to 10carbon atoms.

6. The process according to claim 5 wherein the olefin has up to 6carbon atoms.

7. The process according to claim 6 wherein the olefin is propene.

8. A process for the reaction of 2-methyl-1-propene and an olefincomprising contacting 2-methyl-1-propene and a monoolefin having atleast 3 carbon atoms at a temperature from about 20 C. to about 80 C. inthe presence of a catalytic composition comprising rhenium oxide onmolybdenum oxide on a support or mixtures of rhenium oxide andmolybdenum oxide on a support with said support comprising a majorproportion of alumina, said catalytic composition incorporating fluorideion, in a weight ratio of fluoride ion to metal oxide in the range ofabout 0.0065 :1 to 0.02021, the said catalytic composition comprisingfrom .5 to 1.5 weight percent rhenium oxide and 2.0 to 30 weight percentmolybdenum oxide.

9. The process according to claim 8 wherein the support is at leastpercent alumina.

10. The process according to claim 8 wherein the monoolefin has up to 20carbon atoms.

11. The process according to claim 10 wherein the monoolefin has up to10 carbon atoms.

12. The process according to claim 11 wherein the monoolefin has up to 6carbon atoms.

13. The process according to claim 12 wherein the monoolefin isZ-butene.

14. A process for the dismutation of olefins at a temperature from about20 to about C. in the presence of a catalyst composition consistingessentially of rhenium oxide on molybdenum oxide on a support ormixtures of rhenium oxide and molybdenum oxide on a support with theweight percentages being from .5 to 1.5 percent rhenium oxide and 2.0 to30 weight percent molybdenum oxide and the support comprising at least75 weight percent alumina.

15. The process of claim 14 wherein the said catalyst composition hasincorporated therein fluoride ion in a weight ratio of fluoride ion tometal oxide present in the range of about 0.0065:1 to 0.020: 1.

16. The process of claim 15 wherein the said olefin isZ-methyl-l-propene.

References Cited UNITED STATES PATENTS 3,261,879 7/1966 Banks 2606833,526,676 9/1970 Turner et al 260-683 3,544,647 12/1970 Pennella 260-683FOREIGN PATENTS 1,096,250 12/1967 Great Britain 260683 PAUL M. COUGHLAN,JR., Primary Examiner C. E. SPRESSER, JR., Assistant Examiner

